Problem 2413. Temperature Conversion Utility

There are a few problems on Cody regarding temperature conversion (C to K, C to F, F to C), but none include Rankine. Furthermore, they each involve simple one-liner solutions. For this problem, you are to write a utility function that takes a given temperature and two capital letters designating which temperature scale is being converted to which. For example, T_convertor(100,'C','F') requires 100 degrees Celsius be converted to Fahrenheit.

The test suite includes all 16 possible combinations: C to F, C to R, C to C, C to K, K to F, K to R, etc. (Yes, the redundant combinations are included.)